With the development of data storage technology, various data storage devices can provide users with increasingly high data storage capabilities, and also data access speed has been increased greatly. So far a tier-based distributed storage system has been developed, which may consist of different types of storage devices with different response speeds. Users may store files to different types of storage devices.
When the storage space in a storage system becomes insufficient, more storage devices may be added to the storage system so as to expand the storage capacity. When a user imposes a new requirement on the response speed of the storage system, a storage device that meets the user's new requirement may further be added to the storage system. In addition, an existing storage device in the storage system may be replaced or removed. Although technical solutions have been proposed to migrate data between different types of storage devices, these existing technical solutions have poor flexibility, and the migration efficiency cannot satisfy users' demands. Therefore, how to manage data in a storage system more conveniently and efficiently becomes a research focus.